Devices having a plurality of shelves for heating food products are well known in the art. One common use for such a device is for the preservation of food by dehydration. Examples of such devices are disclosed in U.S. Pat. Nos. 4,190,965 and 4,536,643, which are incorporated herein by reference. Specifically, food to be dried is placed on a plurality of shelves within a cabinet. The dehydrator typically draws air through openings in the base, heats it, and then circulates the air throughout the dehydrator.
Air typically is drawn in and circulated by a motor-driven fan contained within the dehydrator. In order to draw in and circulate sufficient quantities of air, the motor typically drives the fan at relatively high speeds. Consequently, the motor tends to vibrate during operation, which in turn produces noise. Furthermore, conventional motor assemblies in such devices are subject to high labor costs during assembly.
These problems are exacerbated by the fact that the heater coil typically used in dehydrators and the method for mounting the coil obstruct the flow of air. The width of the heater coil itself is often at least one quarter inch thick. Furthermore, the support members used to support the heater are often numerous and bulky in order to provide sufficient support to the heater. As a result, the motor must work even harder to drive the fan at the speed necessary to create sufficient airflow throughout the dehydrator.
Due to the high level of motor activity mentioned above, it can be important that sufficient quantities of air are directed over the motor to prevent it from overheating. This is especially important since many motors typically used in dehydrators are inefficient. One example of such a motor is the shaded pole motor, which runs at only 40-50% efficiency. As a result, the motor can become extremely hot during use. In addition, such air flow over the motor can help heat the air to be circulated within the dehydrator. Currently, much of the air drawn in through base openings is spread throughout the base region before it is directed up and over the motor. As a result, the quantity of the air directed over the motor as compared with that initially drawn in through the base of the device is significantly reduced.
Accordingly, there is a need for a multi-shelf food heating device which provides for more efficient airflow throughout the device. In particular, there is a need for a multi-shelf food heating device having a motor biasing assembly which permits easy assembly of the motor into the device as well as prohibiting movement or vibration of the motor during operation of the device. There is also a need for such an assembly which has a motor cooling configuration for preventing the motor from overheating during use and for assisting in the heating of air to be circulated. There is a further need for a multi-shelf food heating device having a heater and fan assembly which provides for substantially unobstructed airflow within the device.